Method of preparing metallic soaps of fatty acids



Patented Sept. 1, 1953 UNITED STATES ATENT OFFICE METHOD OF PREPARING METALLIC SOAPS OF FATTY ACIDS of New Jersey .No Drawing. Application April 13, 1950, Serial No. 155,796

8 Claims. (01. 260-413) This invention relates to the manufacture of metallic fatty acid soaps. More particularly, it relates to a method of facilitating the preparation of substantially pure-water-insoluble metallic soaps of monocarboxylic aliphatic acids having chain lengths of more than 6 carbon atoms.

Metallic fatty acid soaps are widely used in paints, lubricants, pastes, cosmetics, plastics and other applications. By the existing methods of manufacture, a high degree of purity is obtained with difficulty and many of the above uses would be greatly benefited by greater purity, particularly with respect to the presence of soluble impurities. Such metallic soaps have been made by precipitation from aqueous solutions of soluble metallic salts and water-soluble sodium soaps of a fatty acid. Products so formed are difficult to free from amounts of soluble salts retained. In addition, these soaps have been made by fusion in which case off-colored products generally containing an amount of oxidized or altered fatty acid are obtained in the form of a hard mass which requires grinding. A method of preparing fatty acid compounds particularly basic lead fatty acid compounds is described and claimed in co-pending application, Serial No. 729,402 to Leonard M. Kebrich. The process therein described, however, relies on prolonged mixin of the reactants in the presence of a catalyst comprising an alcohol or an ether and which under ordinary circumstances requires the employment of an intensive mixing device such as a ball mill. As disclosed in co-pending application, Serial No. 729,402, as long as sixteen hours may be required to produce a dibasic lead stearate compound.

This invention has for its principal object, provision of a rapid economic process for the production of metallic fatty acid soaps. This and other objects of theinvention will be apparent from the following, more detailed description thereof.

In its broadest aspects, the present invention contemplates the preparation of insoluble metallic fatty acid soaps by slowly adding and mixing the molten fatty acid with an aqueous suspension of the appropriate metallic oxide or hydroxide under conditions of agitation and in the presence of and under the catalytic influence of one or a combination of a number of organic nitrogenous bases. These bases are characterized by water solubility in excess of 500 grams per liter, an ionization constant greater than 10* a pH value exceeding 9.0 in one-tenth normal aqueous solution, all at room temperature.

The group of such nitrogenous base catalysts includes ammonium hydroxide, simple as well as substituted, primary, secondary and tertiary alkyl amines, alkylol amines, quaternary alkylol ammonium hydroxides, certain cyclic and heterocyclic amines, guanidine and certain amino acids, alkyl diamines and polyalkylpolyamines. Typical members of this group which have been found to be effective in numerous tests are acetamidine; allylamine; 4 amino 2 butanol, 2 aminoethylethanolamine; N amine ethylmorpholine; 2. amino 2 ethyl 1,3 propanediol; 2 amino, 2 methyl, 1 propanol; 2 amino 2 methyl 1,3 propanediol; ammonium hydroxide; arginine; n-butylamine; 1,3 diaminobutane; diethanolamine; diethylamine; diethylaminoethanol; dimethylethanolamine; dimethylisopropanolamine; dipropylenetriamine; N-ethylmorp-holine; guanidine; hydrazine; hydroxylamine; lysine; methallylamine; monoethanolamine; monoethylamine; monoisopropanolamine; monoisopropylamine; morpholine; piperidine; propylenediamine; pyrrolidine; semicarbazide; tetraethanolammonium hydroxide; triethanolamine; triethylamine and triethylenetetramine.

In the procedure of forming the metallic soaps according to the process of this invention a selected nitrogenous base is added to the components mentioned in the form of a free base, in the form of an amine which forms a free base in aqueous media or in the form of a salt which frees the base by a replacement reaction with the metallic hydroxide all in an aqueous system. Stoichiometric proportions of reagents are employed in workable suspensions of from about 10-30% of reactants by weight. The proportion of the nitrogenous base catalyst is generally from about 0.10 to 0.60% by weight of the total system. It will be obvious that more of the catalyst be used but is unnecessary and will not add to the eificiency of the process. It is advantageous to have the metallic oxide in a finely divided condition.

It is preferred particularly in commercial production to add the molten fatty acid slowly to the dispersion of the metallic oxide or hydroxide. This may be accomplished in limited and restricted embodiment of the invention by first forming an emulsion of the fatty acid in warm water then slowly, but continuously, adding this emulsion to a stirred aqueous suspension of the metallic oxide orhydroxide. The common metals which form water-insoluble soaps of fatty acids and which operate in the process of this invention are lithium, calcium, strontium, barium,

magnesium, aluminum, zinc and lead. The fatty acids comprise any of the mono-carboxylic acids containing more than 6 carbon atoms such as caprylic, lauric, myristic, palmitic, stearic, arichidic and behenic, as well as certain of the unsaturated fatty acids which form insoluble soaps, such as ricinoleic and hydroxystearic.

While it is possible to maintain a dispersed phase or emulsion of fatty acid in warm water with high speed. stirring, it is more practical to add a small proportion of an emulsifying agent to maintain a suitable emulsion at a temperature of from about to 10 above the melting point of the fatty acid in question. The rate of addition of the fatty acid emulsion to the oxide suspension, which latter is generally at room temperature but in some instances may be maintained at a temperature of from 35-50 C., is a satisfactory one if the addition is uniformly spread over a period of from about /g to 1 /2 hours. It should be noted that a temperature in excess of 10 or C. above the melting point of the fatty acid is unnecessary and should be avoided for reasons of economy and purity of product.

Ammonium hydroxide is a suitable and economical emulsifying agent for the higher fatty acids. In the process described, the nitrogenous base catalyst functions best if it is added to the oxide suspension, although it may enter the system by reason of having been employed as an emulsifying agent since it has been generally found that the nitrogen base catalyst will so function. In case the nitrogen catalyst is added in the form of a compound such as chloride, sulfate, oxalate, etc., the free base is formed in situ by metathesis with the metallic oxide or hydroxide in aqueous medium. Thus ammonium oxalate, guanidine sulphate or semicarbazide hydrochloride for instance, may be employed as the catalyst forming agent, freeing as a base one of the nitrogenous base catalysts previously mentioned.

When the reaction is completed with proper amounts of material, the product will invariably be found to be a white solid in finely-divided form free from altered and oxidized fatty acid soaps, substantially insoluble in water and characterized by well-defined crystalline structure which gives distinguishable X-ray patterns. The dibasic lead salts made by this method, such as for instance, dibasic lead stearate, plamitate, myristate and laurate, are in addition virtually insoluble in common organic solvents such as alcohol, ether and. chloroform. Furhermore, it was found that these dibasic lead salts having no melting point, invariably decompose before melting at normal pressures. The method of this invention, therefore, enables superior, desirable industrial soaps to be economically formed.

As has been described above, the nitrogenous base may be added either to the metallic oxide suspension, the molten fatty acid emulsion, or both. In any event, its presence in the system during the reaction is essential and the method of introduction of this material may depend in part upon the ingredients employed and on the type of product produced. In cases where the metallic oxide is relatively insoluble or does not readily form a suitable suspension in water, at least part of the nitrogenous base should be added to the oxide suspension before adding the fatty acid. Generally speaking, the emulsion of the fatty acid in warm water is greatly stabilized by the presence of one of these bases in the emulsion so that it is generally desirable to have at least a preferred nitrogenous base material added in combination with the fatty acid.

The following examples are offered as illustrative embodiments of this invention:

EXAMPLE I Calcium stearate 5.60 g. of calcium oxide were suspended in 300 ml. of water at 55 0., 56.9 g. of C. P. stearic acid were then melted and 350 ml. of warm water at a temperature of about 70 C. was added thereto. The acid-water mixture was then agitated and emulsified with the addition of 0.75 g. of diethanolamine and the emulsion gradually added to the agitated lime slurry over a period of 2 hours. The white insoluble product formed was filtered and dried, and found to contain 9.2% CaO and 1.18% CO2 with a specific gravity of 1.07 and a refractive index of 1.52-1.53.

EXAMPLE II Zinc Zaurate 27.5 g. of C. P. zinc oxide were suspended in 150 ml. of water to which had been added 0.5 g. of morpholine. An emulsion of 140.6 g. of commercial grade lauric acid, 700 ml. of water and 0.5 g. of morpholine was prepared and maintained at a temperature of 65 C. This emulsion was gradually added to the warmed zinc oxide suspension maintained at a temperature of 55 C. over a period of A of an hour with constant agitation. The white zinc laurate product was filtered and dried, and found to contain 167% ZnO, had a specific gravity of 1.15 and a refractive index of about 1.53.

EXAMPLE III Dibasic lead stearate 600 g. of finely powdered lead monoxide were suspended in 1500 ml. of water while the suspension was agitated and heated to 60 C. and 8.25 g. of triethanolamine added. Then 500 g. of commercial grade stearic acid were melted and mixed with constant stirring with 4500 ml. of water at about 65 C. 7.5 g. of triethanolamine were then added to effect emulsification and the hot emulsion of stearic acid was slowly and continuously added to the agitated litharge suspension over a period of about 4 hours, while the temperature was maintained at about 60 C. The white powdered insoluble product was filtered and dried and was found to contain 55.5% lead monoxide. It was the dibasic lead salt of a mixture of stearic, palmitic and oleic acids.

EXAMPLE IV Dibasic lead stearate 120 g. of finely divided litharge were suspended in 300 ml. of water and 0.40 g. of monoethanolamine was added thereto and. agitated with a power driven paddle in a glass reaction vessel at room temperature. Then g. of technical grade stearic acid was melted and placed in a glass reaction vessel containing 700 ml. of water, heated to 60 C. and while under constant agitation, 1 g. of ammonium hydroxide was added to effect emulsification of the fatty acid. The warm stearic acid emulsion was then gradually added to the agitated litharge suspension over a period of 30 minutes after which time the litharge was completely converted to a white, insoluble powdery substance. The product was filtered and was found on analysis to contain 56.3% PhD and 43.7% combined stearic, palmitic and oleio acids free from oxidized fatty acids, and had an apparent density of 3.20 g./cm. was insoluble in water, alcohol, ether and chloroform, was pure white in color and in finely-divided form.

Certain of the unsaturated fatty acids which are solids at room temperature and which produce substantially water-insoluble soaps with the above-mentioned metals may also be prepared by the method of this invention as the following example will show.

The preparation of normal lead steal-ate is readily accomplised by following the procedure outlined in Example IV and changing the relative amount of stearic acid. For instance, by employing 40 g. of litharge in place of 120 g. of litharge in 300 ml. of water, normal lead stearate will be formed by the process given in Example IV.

EXAMPLE V Barium ricinoleate 47.9 g. of barium hydroxide containing 55.2% Ba(OH)2 were suspended in 300 ml. of water at 23 C. 100 g. of castor oil fatty acids were agitated with 400 ml. of water at 25 C. and 4 g. of concentrated ammonium hydroxide containing 28-29% NHB were added thereto. The emulsified castor oil fatty acids were then gradually added to the barium hydroxide suspension over a period of 1 hours. The white insoluble product formed was filtered and dried, and found to be barium ricinoleate.

It will be noted that in Examples 3 and 4 the proportions of PbO in the dibasic lead salt form are given as 55.5% and 56.3%, respectively. This difference is due to a variation in the relative proportions of the three fatty acids present in the commercial grade stearic acid. When pure stearic acid was used, the dibasic lead salt was found by analysis to contain 54.9% PbO. In all cases, however, it was confirmed by analysis as well as X-ray patterns and other properties that the entire yield of product consisted of the unaltered fatty acid salt, free from oxystearates which are generally obtained by more drastic operating conditions such as the employment of elevated temperatures, for instance.

While this invention has been described and illustrated by the examples shown it is not intended to be strictly limited thereto and other variations and modifications may be employed within the limits of the following claims.

We claim:

1. A method for production of a metallic soap of a fatty acid containing more than 6 carbon atoms which comprises forming an aqueous emulsion of said acid in molten condition and slowly adding said emulsion to an agitated aqueous suspension of a compound selected from the group consisting of oxides and hydroxides of lithium, calcium, strontium, barium, magnesium, aluminum, zinc and lead in the presence of an amount between 0.1 and 0.6% of the total system of a nitrogenous base catalyst characterized by water solubility in excess of 500 grams per liter, an ionization constant of greater than 10' and a pH value exceeding 9.0 in one tenth normal solution all characteristics at room temperature thereby forming a metallic soap of said fatty acid in finely divided solid form.

2. A method according to claim 1 in which the nitrogenous base is a compound selected from the group consisting of acetamidine; allylamine; 4 amino 2 butanol; 2 aminoethylethanolamine; N-amine ethylmorphoiine; 2 amino 2 ethyl 1,3, propanediol; 2 amino, 2 methyl, 1 propanol; 2 amino 2 methyl 1, 3 propanediol; ammonium hydroxide; arginine; n-butylamine; 1,3 diaminobutane; diethanolamine; diethylamine; diethylaminoethanol; dimethylethanolamine; dimethylisopropanolamine; dipropylenetriamine; N-ethylmorpholine; guanidine; hydrazine; hydroxylamine; lysine; methallylamine; monoethanolamine; monoethylamine; monoisopropanolamine; monoisopropylamine; morpholine piperidine; propylenediamine; pyrrolidine; semicarbazide, tetraethanolammonium hydroxide; triethanolamine; triethylamine and triethylenetetramine.

3. A method according to claim 1 in which the nitrogenous base is ammonium hydroxide.

i. A method according to claim 1 in which the nitrogenous base is monoethanolamine.

5. A method according to claim 1 in which the nitrogenous base is morpholine.

6. A method according to claim 1 in which the nitrogenous base is monoethylamine.

'7. A method according to claim 1 in which the nitrogenous base is formed in situ by using ammonium sulphate.

8. A method according to claim 1 in which the nitrogenous base is initially present at least in part in the molten fatty acid emulsion.

LEONARD M. KEBRICI-I. ADRIAN R. PITROT.

References Cited in the file of this patent UNITED STATES PATENTS Number 

1. A METHOD FOR PRODUCTION OF A METALLIC SOAP OF A FATTY ACID CONTAINING MORE THAN 6 CARBON ATOMS WHICH COMPRISES FORMING AN AQUEOUS EMULSION OF SAID ACID IN MOLTEN CONDITION AND SLOWLY ADDING SAID EMULSION TO AN AGITATED AQUEOUS SUSPENSION OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF OXIDES AND HYDROXIDES OF LITHIUM, CALCIUM, STRONTIUM, BARIUM, MAGNESIUM, ALUMINUM, ZINC AND LEAD IN THE PRESENCE OF AN AMOUNT BETWEEN 0.1 AND 0.6% OF THE TOTAL SYSTEM OF A NITROGENOUS BASE CATALYST CHARACTERIZED BY WATER SOLUBILITY IN EXCESS OF 500 GRAMS PER LITER, AN IONIZATION CONSTANT OF GREATER THAN 10-9 AND A PH VALUE EXCEDING 9.0 IN ONE TENTH NORMAL SOLUTION ALL CHARACTERISTICS AT ROOM TEMPERATURE THEREBY FORMING A METALLIC SOAP OF SAID FATTY ACID IN FINELY DIVIDED SOLID FORM. 